(1) Field of the Invention
The invention relates to a method of copper stripping in the fabrication of integrated circuits, and more particularly, to a method of endpoint detection for controlled copper stripping in the manufacture of integrated circuits.
(2) Description of the Prior Art
In the manufacture of integrated circuits, copper stripping is required in a number of situations: after blanket copper deposition on a bare silicon wafer, after copper seed layer deposition in a damascene process, after electroplated copper deposition in a damascene process, or after copper chemical mechanical polishing (CMP), for example. Wet stripping of copper generally requires an extensive duration, or overstripping, as a safeguard to be sure that all of the copper is removed. Overstripping incurs a high cost. It is necessary to periodically measure the remaining copper thickness to determine when to stop the stripping process. This is time-consuming. It is desired to provide an endpoint detection system for copper stripping.
U.S. Pat. No. 5,836,805 to Obeng discloses a method of examining the waste slurry of a chemical mechanical polishing (CMP) process to determine the endpoint. Conductivity, luminescence, or particulate mass are measured depending upon the material being polished. U.S. Pat. No. 4,774,101 to Harris et al controls the contents of an electroless copper plating bath by optical means. U.S. Pat. No. 4,286,965 to Vanhumbeeck et al also controls the contents of an electroless copper plating bath. The amount of copper in the bath is measured by colorimeter. U.S. Pat. No. 4,749,552 to Sakisako et al automatically maintains the density of an etching liquid used to etch a specific quantity of copper. Measurements of the etching liquid""s contents are made by titration.
A principal object of the present invention is to provide an effective and very manufacturable method of endpoint detection for copper stripping in the fabrication of integrated circuit devices.
Another object of the invention is to provide an endpoint detection system for copper stripping on a single wafer system or a batch wafer system.
Yet another object of the invention is to provide an endpoint detection system for copper stripping using a colorimetric or spectrophotometric analysis of the change in concentration of a component.
Yet another object of the invention is to provide novel compounds or chemicals for use in an endpoint detection system for copper stripping.
Yet another object of the invention is to provide novel compounds or chemicals for use in an endpoint detection system for copper stripping using a colorimetric or spectrophotometric analysis of the change in concentration of the novel compounds or chemicals.
In accordance with the objects of this invention an endpoint detection system for copper stripping using a colorimetric or spectrophotometric analysis of the change in concentration of a component is achieved. Wet copper stripping chemicals are used to strip copper from a wafer whereby an eluent is produced. The eluent is continuously analyzed by colorimetric or spectrophotometric analysis for the presence of copper. The copper stripping process is stopped when the presence of copper is no longer detected.
Also in accordance with the objects of the invention, novel compounds or chemicals for use in an endpoint detection system for copper stripping using a colorimetric or spectrophotometric analysis of the change in concentration of the novel compounds or chemicals are provided. A composition of matter that serves as an indicator of the presence of copper by colorimetric analysis comprises: 1) Fast Sulphon Black F indicator and an ammonium ion-containing solution or 2) a complexing agent, comprising a diamine, an amine macrocycle, or a monoamine.